James "Jemmy" Johnston was born 1760 in County Antrim, Ireland, the son of David Johnstone, who died in Ireland, and Sarah Meek, who died in South Carolina.  After coming to South Carolina he married his first cousin Mary Johnston in 1780. 

James "Jemmy" Johnston was a real hero of the American Revolution and in Vol. III, pages 206-215, "Women of the American Revolution ," Mrs. Ellet relates the following:

"James Johnston with his uncle Matthew Johnston (Mary's father) took part in the Cherokee uprising in 1776 and were at Ft. Moultrie when it was attacked and at the siege of Savannah.  They were with McClure in the action at Mobley's, Williamson's, rocky Mount, Hanging Rock, and Carey's Fort.  They were with Sumter's army at the surprise on Fishing Creek, and made their escape with others, picking up their guns as they fled.  After they had passed up the road some distance, they were charged upon by a troop of dragoons, and Matthew Johnston was shot down and killed.  James turned, and taking deliberate aim at one of the troop, fired, and saw him fall from his horse.  At the same instant a ball reaching him, struck against a pocket book in his vest, which turned its course under his ribs, inflicting a severe wound.  The dragoons, seeing one of their members fall, wheeled about; the freed horse ran toward the spot where James lay unable to move, and his friend Samuel Morrow, a man of great strength, caught the animal, flung Johnston upon him and mounting himself behind, bore him safely to Charlotte.  James recovered from his wound and afterwards was known as "Adjt. Jemmy Johnston" under Col. Lacy; he was promoted and served as captain in the State troops; hew was at the battle of Kings Mountain and with General Sumter till the close of the war."

"On the first of August Sumter attempted to carry Rocky Mount in three assaults, without success.  He then ordered Col. Neel to storm a loop holed fortified house in which the British were strongly posted.  Neel was killed and the storming party repulsed.  Then Sumter called for two men to volunteer to burn the building and in the force of almost certain death Col. William Hill and Adjt. "Jemmy" Johson (spelled wrong!) made the attempt and running directly in front of the portholes and guns of the fort, threw the burning, lightwood faggots on top of the house and set it afire.  They escaped, their clothes riddled with bullets and their hair singed, but a heavy rain storm put out the fire and Sumter ordered his force to withdraw to Landsford."

"It would not be worth while to speak of the spirited attack made by a part of Sumter's force on the British post at rocky Mount.  Turnbull, in command of that post with British and Tories made out to maintain his position with inconsiderable loss.  The hope in the attack consisted in firing a stack of hay and so communicating the flames to the fort.  But the unruly wind blew the wrong way.  And how often life do we find that we fail because the wind is perverse or intractable?  James Johnston, commonly known as Adjutant Johnston, was the Whig hero on this occasion.  Hew wore then the blade which graced the side of his grandfather at the Siege of Derry."

James Johnston was a planter and constable.  He died in 1797 from complications of wounds received in the War.  Mary survived him over fifty years.